Synthesis of non-covalent BODIPY-metalloporphyrin dyads and triads

Article abstract of DOI:10.1016/j.tet.2011.11.048

Boron-dipyrromethenes (BODIPY) containing oxypyridine substituents at 3- and 3,5-positions and metalloporphyrins (Zn(II), Ru(II)) were used to synthesize four non-covalent BODIPY-metalloporphyrin dyads and four BODIPY- metalloporphyrin triads assembled us

Full text of DOI:10.1016/j.tet.2011.11.048

Tetrahedron 68 (2012) 830e840
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of non-covalent BODIPYemetalloporphyrin dyads and triads
*
Tamanna K. Khan, Mangalampalli Ravikanth
Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Boron-dipyrromethenes (BODIPY) containing oxypyridine substituents at 3- and 3,5-positions and
metalloporphyrins (Zn(II), Ru(II)) were used to synthesize four non-covalent BODIPYemetalloporphyrin
dyads and four BODIPYemetalloporphyrin triads assembled using metalepyridine ‘N’ interaction. The
formation of BODIPYemetalloporphyrin assemblies was confirmed by 1D and 2D NMR methods and X-
ray crystal structure obtained for one of the BODIPYemetalloporphyrin dyad. In 1H NMR, the signals of
oxypyridine group(s) of BODIPY unit showed significant upfield shifts supporting the coordination of
oxypyridine group of BODIPY unit to metalloporphyrin unit. The NMR study also indicated that Zn(II)
porphyrin forms relatively weak BODIPYeZn(II) porphyrin conjugates, whereas Ru(II) porphyrin forms
strong BODIPYeRu(II) porphyrin conjugates. The X-ray structure solved for BODIPYeZn(II)porphyrin
dyad revealed that the Zn(II) porphyrin coordinated to the BODIPY unit obliquely and the angle between
the Zn(II) porphyrin and the pyridyl ring is 70ꢀ. The absorption properties of stable BODIPYeRu(II)
porphyrin conjugates showed the overlapping absorption features of both the components and the
fluorescence studies indicated that the BODIPY unit emission was significantly quenched on coordination
with RuTPP(CO) unit. The electrochemical studies exhibited the features of both BODIPY and metal-
loporphyrin units in dyads and traids.
Received 23 September 2011
Received in revised form 16 November 2011
Accepted 18 November 2011
Available online 25 November 2011
Keywords:
Boron-dipyrromethenes
Metalloporphyrins
Metalepyridyl coordination
BODIPYemetalloporphyrin assemblies
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
properties. Recently Dehaen and co-workers15e19 reported the syn-
thesis of 3,5-dihalo functionalized BODIPYs, which gives an access to
The metalepyridine interactions play a very important role in
generating supramolecular architectures that include squares, mac-
rocycles, catenanes, cages, and tubes.1e5 Most of these metale
pyridine based supramolecular structures were shown to be stable
both in solution and solid state and are characterized thoroughly by
NMR and X-ray crystallography.6,7 The prime advantage of using
pyridine is that it is one of the versatile ligand, which can form com-
plexes with various transition metal ions. Our group is interested in
the design and synthesis of new boron-dipyrromethene dyes for
various applications.8e11 Boron-dipyrromethenes (4,4-difluoro-4-
bora-3a,4a-diaza-s-indacene, BODIPY) are excellent fluorophores
and have been used in various research fields as labeling reagents,
fluorescent switches, chemosensors, light harvesting systems, and
dye sensitized solar cells because of their advantageous photophysical
properties, such as photostability, high absorption coefficients, and
high fluorescence quantum yields.12e14 BODIPY dyes are amenable to
modifications, which allow fine tuning of properties by introduction
of suitable substituents at appropriate positions of the dipyrrome-
thene framework. There are several positions on BODIPY chromo-
phore where substituents can be introduced to tune the electronic
synthesize a wide range of 3,5-disubstituted BODIPYs containing ox-
ygen, carbon, nitrogen, and sulfur centered nucleophiles. We adopted
this approach and treated 3,5-dibromo BODIPYs with 2-, 3-, and 4-
hydroxypyridines in CH3CN in the presence of Cs2CO3 under very
mild conditions.20 The 2- and 4-hydroxypyridines on reaction with
3,5-dibromo BODIPYs in the presence of base in CH3CN at refluxing
temperature afforded 3,5-bis(pyridone)BODIPYs, whereas 3-
hydroxypridine under same reaction conditions with 3,5-dibromo
BODIPY gave 3,5-bis(oxypyridine)BODIPYs. These two classes of
BODIPYs are different from each other in their spectral, electro-
chemical, and photophysical properties significantly.20 Although, the
3,5-bis(oxypyridine) BODIPYs did not show much alteration in prop-
erties compared to the reference 3,5-unsubstituted meso-aryl boron-
dipyrromethene,21 these BODIPYs containing decorated oxypyridine
groups are very useful building blocks to synthesize BODI-
PYemetalloporphyrin conjugates by using non-covalent metale
pyridine interactions, which is explored in this paper. A simple stoi-
chiometric reaction between BODIPY with oxypyridine substituents
and metalloporphyrin (ZnII and RuII) resulted in the formation of
BODIPYemetalloporphyrin assemblies 5e12 in high yields. 1D, 2D
NMR, and X-ray crystallography techniques were used to confirm the
formation of BODIPYemetalloporphyrin dyads 5e8 and triads 9e12.
Thespectral andelectrochemicalpropertiesindicatedthattheBODIPY
* Corresponding author. Tel.: þ91 022 2576 7176; fax: þ91 022 2576 7152; e-mail
address: ravikanth@chem.iitb.ac.in (M. Ravikanth).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.11.048

T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
831
and metalloporphyrin components interact weakly and retain their
individual characteristic features in these assemblies.
The compounds 1e4 containing one and two oxypyridine sub-
stituents at 3- or 3,5-positions were used as building blocks to
construct supramolecular architectures by treating them with
metalloporphyrins, such as ZnTPP and RuTPP(CO)(EtOH). The non-
covalent dyads, such as 5e8 were synthesized as shown in the
Scheme 1. The dyads 5 and 6 were synthesized by treating 1 and 2,
respectively, with 1 equiv of ZnTPP in CHCl3 for 30 min at room
temperature and the crude compounds were recrystallized using
CHCl3/n-hexane. The dyads 5 and 6 are not stable for column
chromatographic purification on silica indicating that the compo-
nents BODIPY and ZnTPP are weakly bonded in these dyads. On the
other hand, the dyads 7 and 8 were prepared by reacting 1 equiv of
1 and 2, respectively, with 1 equiv of RuTPP(CO)(EtOH) at 80 ꢀC for
overnight. The progress of the reaction was followed by TLC anal-
ysis. The crude reaction mixtures were subjected to column chro-
matographic purification on silica using petroleum ether/
dichloromethane and afforded the red colored dyads 7 and 8 in
55e70% yields.
2. Results and discussion
The mono- and dioxypyridine substituted meso-aryl BODIPY
building blocks 1e4 used for the synthesis of non-covalent
BODIPYemetalloporphyrin assemblies are shown in the Chart 1.
The 3,5-di(oxypyridine) meso-anisyl BODIPY
3
and 3,5-
di(oxypyridne) meso-furyl BODIPY 4 were synthesized by fol-
lowing our earlier reported method.20 The mono oxypyridinyl
substituted BODIPYs, 3-(oxypyridine) meso-anisyl BODIPY 1 and
3-(oxypyridine) meso-furyl BODIPY 2 were prepared by treating
1 equiv of the corresponding 3-bromo BODIPYs 13 and 14, re-
spectively9 with 1 equiv of 3-hydroxypyridine in CH3CN in the
presence of Cs2CO3 at refluxing temperature for 1 h. The crude
reaction mixtures were purified by silica gel column chroma-
tography and afforded mono oxypyridinyl substituted meso-aryl
N
N Zn
N
N
R
N
N
N
NZn
N
N
B
O
F
F
CHCl3
N
OMe
R =
R =
; 5
; 6
R
B
O
N
N
O
F
F
CO
N
N Ru
N
N
R
B
N
HOEt
CO
N
N
N
NRu
N
N
O
80oC, Overnight
Toluene,
F
F
N
OMe
R =
R =
; 7
; 8
O
Scheme 1. Synthesis of dyads 5e8.
BODIPYs 1 and 2 in 60e70% yields. The compounds 1 and 2 are
freely soluble in common organic solvents and confirmed by
molecular ion peak in HRMS mass spectra and clean 1H, 19F, and
11B NMR spectra. The absorption and fluorescence properties of
compounds 1e4 are in line with the general behavior of pyrrole
unsubstituted meso-aryl BODIPY, such as meso-phenyl boron
dipyrromethene21 indicating that the oxypyridine substituent(s)
at 3- and 3,5-positions did not alter the electronic properties of
BODIPY core.
The dyads 5e8 were confirmed by molecular ion peak in ES-MS
mass spectra. However, the formation of all four dyads 5e8 were
unambiguously confirmed by a detailed 1D and 2D NMR studies.
The comparison of 1H NMR spectra of dyads 5 and 7 and a BODIPY
building block 1 is shown in Fig. 1a along with proton assignments.
The assignments were made on the basis of the resonance position
and intensity data as well as the proton-to-proton connectivity
revealed in the 1He1H COSY spectrum shown for dyad 6 in Fig. 1b.
The relevant 1H NMR data of all BODIPYemetalloporphyrin dyads

832
T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
Fig. 1. (a) Comparison of 1H NMR spectra for compounds 5, 7, and 1 (b) 1He1H COSY-NMR spectrum for compound 6 in selected region recorded in CDCl3.
and the corresponding monomers are presented in Table 1. In 1H
NMR, the signals corresponding to both the components, BODIPY
and metalloporphyrin are present with alterations in their chem-
ical shifts. In 1H NMR, the metalloporphyrin component reso-
nances in the dyads 5e8 did not show much changes in their
chemical shifts compared to corresponding monomeric metal-
loporphyrins but the significant changes in the chemical shifts
were observed for BODIPY units because of ring current effect of
metalloporphyrin, which cause changes in chemical shifts of pro-
tons located near its plane. As clear from the Fig. 1b and data in
Table 1, the pyridyl protons, which are closer to porphyrin ring
experienced significant upfield shifts compared to pyrrole protons
of BODIPY core. It is noted that only type a pyrrole proton expe-
rienced 1e2 ppm upfield shift, whereas all other pyrrole protons of
BODIPY core did not show any shift. On the other hand, the pyridyl
protons of type cef, which were identified by the proton connec-
tivity pattern in 1He1H COSY spectra experienced significant up-
field shifts compared to the pyridyl protons of the free BODIPY
building block. For example, in the dyad 5, the porphyrin ring
current shift of BODIPY protons of type cef is Δ
BODIPY 1), which is w5.1 for type e,f-protons and w1.1 ppm for
d
¼
d
(dyad 5)ꢁ
d (free
type c,d-protons.

T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
833
Table 1
1H NMR chemical shift values (in ppm) for compounds 1e10 recorded in CDCl3
Sr. no.
a
b
a0
b0
g
f1
f2
f3
c
d
e
f
1
5
7
2
5.76 (d) 6.68 (s) 6.51 (s)
4.29 (d) 6.69 (d) 6.50 (s)
3.56 (d) 6.63 (d) 6.55 (s)
5.81 (d) 7.28 (d) 6.68 (s)
6.94 (d) 7.80 (s)
7.65 (d)
6.50 (s)
6.10 (d)
7.39e7.43 (m) 8.56 (d) 8.67 (s)
5.85e5.88 (m) 3.43 (s) 3.30 (s)
6.87 (d) 7.65e7.75 (m)
6.90 (d) 7.65e7.72 (m)
7.49 (d) 7.81 (s)
5.29 (m)
1.48 (d) 1.41 (s)
7.07 (d) 6.54e6.52 (m) 7.81 (s) 7.65e7.67 (m) 7.40e7.43 (m) 8.57 (d) 8.67 (d)
6
8
3
9
11
4
10
12
4.24 (d) 7.17 (d) 6.52e6.53 (m) 7.32 (d) 7.69 m
3.66 (d) 7.15 (d) 6.56e6.57 (m) 7.36 (d) 7.67e7.74 (m) 6.99 (d) 6.75 (m)
6.99 (d) 6.72 (s)
7.82 (s) 6.39 (d)
7.85 (s) 6.10 (d)
7.63 (d)
5.70e5.74 (m) 2.93 (d) 2.72 (d)
5.29e5.33 (m) 1.48 (d) 1.44 (d)
5.74 (d) 6.81 (d)
4.27 (d ) 6.60 (d)
3.56 (d) 6.56 (d)
5.79 (d) 7.30 (d)
4.62 (d) 7.10 (d)
3.66 (d) 7.04 (d)
7.36 (d)
8.52 (s) 8.66 (s)
3.20 (br s)
1.43 (s)
8.52 (d) 8.65 (d)
4.23 (br s)
6.40 (d)
6.10 (d)
5.79e5.8 (m)
5.23e5.29 (m)
7.36 (d)
6.07e6.1 (m)
5.22e5.26 (dd)
6.97 (d) 6.65e6.67 (m) 7.75 (s) 7.62 (m)
6.85 (d) 6.73 (s)
6.81 (d) 6.78 (s)
7.81 (s) 6.62 (d)
7.87 (s) 5.98 (d)
1.42e1.45 (m)
The significant shift observed for type e,f-protons is because of
their close proximity to the metalloporphyrin ring compared to
type c,d-protons. Similar observations were made for BODIPY-
RuTPP(CO) dyads 7 and 8. However, in BODIPYeRuTPP(CO) dyads
furyl ring (plane 2) and the plane defining various dipyrrin atoms
(plane 1) in compound 2 is w31ꢀ, which is almost remained same
(w33ꢀ) in compound 6. It has been shown recently that the meso-
furyl ring, because of its smaller size orients more toward the boron
dipyrrin ring resulting in the decrease of the dihedral angle com-
pared to meso-aryl substituted BODIPYs.22 Furthermore, in com-
pound 2, the plane 3 defining pyridyl group is at an angle of 82ꢀ
w.r.t. boron-dipyrrin (plane 1), which is substantially reduced to
42ꢀ in compound 6 because of the coordination of pyridyl ‘N’ with
Zn(II) porphyrin. The angle between pyridyl plane 3 and plane 6
defining porphyrin ring is 70ꢀ indicating that pyridyl group is not
completely perpendicular to the plane of the metalloporphyrin. The
7 and 8, the pyridyl protons of type c,d, (Δ
d
¼w1.5) and type e,f
(Δd
¼w7.1) experienced more upfield shifts compared to dyads 5
and 6 supporting that the BODIPY and RuTPP(CO) units were
bonded more strongly in these dyads (Supplementary data).
The BODIPYemetalloporphyrin triads 9e12 (Chart 2) were also
synthesized by adopting the same approach used for dyads 5e8.
The triads 9e12 showed the corresponding molecular ion peak in
ES-MS mass spectra confirming their identities. Further confirma-
tion for the formation of triads 9e12 was obtained by detailed 1D
and 2D NMR studies (Supplementary data). Because of the sym-
metric arrangement, the 1H NMR spectra of triads 9e12 are very
simple unlike dyads 5e8. A systematic titration of ZnTPP with
BODIPY 3 was carried out in CDCl3 and the changes in the 1H NMR
are shown in Fig. 2a. The ZnTPP equivalents were varied gradually
from 0 to 2 equiv and the changes observed in the 1H NMR clearly
supports the formation of triad 9. As clear from the Fig. 2a, on in-
creasing the addition of ZnTPP to BODIPY 3 up to 2 equiv, the
pyrrole protons of type ‘a’ and pyridyl protons of type cef steadily
experiences upfield shift and maximum shifts were observed on
complete addition of 2 equiv of ZnTPP confirming the formation of
triad 9. This was also confirmed by recording 1D and 2D NMR
spectra for the triad 9, which was isolated by treating 1 equiv of
BODIPY 3 with 2 equiv of ZnTPP in CHCl3 at room temperature
followed by recrystallization (Fig. 2b). The triads 11 and 12, which
were isolated by column chromatography also showed similar
upfield shifts of pyridyl protons. However, the pyridyl protons
appeared at more upfield because of strong coordination of Ru(II)-
pyridyl ‘N’ in these triads (Supplementary data). Thus, 1D and 2D
NMR studies clearly supported the formation of dyads 5e8 and
triads 9e12.
ꢀ
Zn-pyridyl ‘N’ bond length is 2.21 A, which is in the same range as
those of similar systems reported earlier.23e25 The Zn atom lies
slightly above the basal plane defined by the four nitrogen atoms
ꢀ
(plane 6) with the deviation of 0.308 A.
There are also slight alterations in bond lengths and bond angles
in compound 6 w.r.t. compound 2 due to coordination of BODIPY
pyridyl ‘N’ with Zn(II)porphyrin.
Since the BODIPYeZnTPP based dyads 5/6 and triads 9/10 are not
stable at low concentration, the absorption properties of only the
stable BODIPYeRuTPP(CO) based dyads 7/8 and triads 11/12 and
their corresponding monomers were studied in CHCl3 and the data
are presented in Table 3. The comparison of dyad 7 and triad 11
recorded at the same concentration in CHCl3 is shown in Fig. 4a. In
general, the pyridyl substituted boronedipyrromethene complexes20
1e4 show a strong absorption band corresponding to S0/S1 transi-
tion in 500e540 nm region and RuTPP(CO)(EtOH) exhibits one
strong Soret band at 413 nm and two weak Q-bands at 530 and
570 nm. Asclear fromtheFig. 4aand thedatapresented inTable 3 that
the dyads 7/8 and triads 11/12 showed bands corresponding to both
the components with negligible variation in their peak maxima
compared to their corresponding monomers. The emission proper-
ties of dyads 7/8 and triads 11/12 were studied by steady state fluo-
rescence technique and relevant data are included in Table 3. The
comparison of steady state fluorescence spectra of triad 11 and
BODIPY monomer 3 recorded in CHCl3 using excitationwavelength of
488 nm is shown in Fig. 4b. The BODIPY monomer 3 is decently
fluorescent with a quantum yield of 0.58. However, in triad 11, the
BODIPY fluorescence was quenched by 93%. Similarly, the BODIPY
emission in dyads 7/8 and triad 12 was also quenched significantly.
These results indicated that the ruthenium ion, which coordinated to
pyridyl ‘N’ of BODIPY unit quenches the singlet state of the BODIPY
unit by enhancing the spin-forbidden deactivation processes.
The electrochemical properties of dyads 5e8 and triads 9e12
along with their corresponding monomers were followed by cyclic
voltammetry in CH2Cl2 using tetrabutylammonium perchlorate as
a supporting electrolyte. A comparison of cyclic voltammograms of
dyad 5 and its constituted monomers 1 and ZnTPP is shown in
Fig. 5 and data are presented in Table 4. In dyads 5e8 and triads
9e12, we observed three reductions corresponding to BODIPY and
We fortunately obtained the crystal structure of dyad 6, which
confirmed the formation of this kind of BODIPYemetalloporphyrin
dyads 5e8 and triads 9e12. The single crystals of dyad 6 and its
corresponding free BODIPY monomer 2 were obtained from n-
hexane/dichloromethane on slow evaporation over a period of one
week. Both compounds crystallized in the triclinic crystal system
with the same Pꢁ1 space group. Fig. 3 shows the crystal structures
of compounds 2 and 6 and the important bond lengths and angles
are presented in Table 2. In compound 2, the two pyrrole rings and
the six membered ring containing boron are almost in the same
plane like any other BODIPY dye.21 However, in compound 6, be-
cause of Zn(II)porphyrin coordination with the oxypyridine group
of BODIPY, the two pyrrole rings (planes 4 and 5) are not in one
plane and they are oriented at 15ꢀ with each other (Supplementary
data).The six membered boron containing ring in compound 6 is
distorted and the boron atom is slightly deviated from the main
dipyrrin framework. The angle between the plane defining meso-

834
T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
Fig. 2. (a) 1H NMR titration of 3 with addition of increasing equivalents of ZnTPP (0e2 equiv). (b) 1He1H COSY NMR spectrum of compound 9 in selected region recorded in CDCl3.
metalloporphyrin units and two oxidations corresponding to only
metalloporphyrin unit. For example, the dyad 5 showed three re-
ductions at ꢁ0.85, ꢁ1.23, and ꢁ1.68 V and two oxidations at 0.80
and 1.1 V. The first reduction at ꢁ0.85 V was due to BODIPY unit 1
and the two reductions and two oxidations were because of ZnTPP
unit. A close inspection of data of dyads 5e8 and triads 9e12 in-
dicate that the potentials of dyads 5e8 and triads 9e12 were in the
same range of their constituted monomers. Thus, the electro-
chemical studies of dyads 5e8 and triads 9e12 indicate that the
BODIPY and metalloporphyrin sub-units in dyads and triads in-
teract very weakly.
3. Conclusions
Four BODIPYemetalloporphyrin dyads 5e8 and four BODI-
PYemetalloporphyrin triads 9e12 were synthesized by treating
BODIPYs containing oxypyridine substituents at 3- and 3,5-
positions, respectively, with metalloporphyrins (Zn(II) and Ru(II))
utilizing pyridineemetalloporphyrin interaction. The formation of
dyads 5e8 and triads 9e12 were confirmed by significant upfield
shifts of pyridyl protons due to the ring current effect of metal-
loporphyrin. The NMR study also revealed that BODIPY-RuTPP(CO)
dyads 7/8 and triads 11/12 are more stable than BODIPY-ZnTPP

T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
835
Fig. 3. X-ray crystal structures of compounds (a) 2 and (b) 6. Selected mean planes for the compound 2 and 6 also shown at the bottom.
dyads 5/6 and triads 9/10. The X-ray structure obtained for BODIPY-
Zn(II)porphyrin dyad 5 indicated that the BODIPY unit in conjugate
5 is slightly distorted compared to free BODIPY and it is obliquely
oriented with metalloporphyrin unit. The absorption and electro-
chemical studies indicated that the conjugates exhibit features of
both the constituted monomeric units. The emission of BODIPY
unit in dyads and triads was significantly quenched because of
RuTPP(CO) unit, which enhances the non-radiative deactivation
processes.
Table 2
Selected bond distances (Ǻ) and bond angles (ꢀ) for compounds 2 and 6
Bond Length/Torsion angles
2
6
B1eN1
B1eN2
B1eF1
B1eF2
F1eB1eF2
N1eB1eN2
C6eO1eC9
C1eO2eC14/C13eO2eC14
C(2)eH(2)
C4eC5eC10
C17eN3eC18
O(1)eC(6)eC(5)eC(4)
ZneN3
1.53
1.55
1.38
1.39
108.46
106.28
106.22
117.71
0.95
120.16
116.01
31.6
d
1.57
1.51
1.41
1.37
108.87
106.18
111.29
120.08
0.95
119.47
119.93
33.4
Table 3
Photophysical data for dyads 7/8 and triads 11/12 along with their reference com-
pounds recorded in CHCl3
Compound labs (nm)
lem (nm) FF BODIPY (%Q)a
1
2
3
4
504 (4.7)
526 (4.7)
516 (4.9)
538 (4.5)
521
573
537
583
d
0.10
0.11
0.58
0.15
d
d
d
d
d
RuTPP
7
413 (5.5), 531 (4.5), 569 (sh)
413 (5.4), 505 (4.9), 534 (4.3), 521
569 (sh)
d
0.028
70%
2.21
ZneN4
ZneN5
ZneN6
ZneN7
d
2.05 (4)
2.02 (5)
2.07 (4)
2.04 (5)
0.308 (5)
8
11
12
413 (5.3), 531 (4.5), 569 (sh)
413 (5.5), 518 (4.9), 568 (sh)
413 (5.6), 535 (4.8), 570 (sh)
570
537
583
0.033
0.035
0.028
70%
93%
81%
d
d
d
a
(%Q) denotes percentage of quenching of fluorescence quantum yield of BODIPY
Zn displacement
d
unit.

836
T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
OMe
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
(a)
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
O
N
N
N
N
B
O
B
O
375
400
425
450
475
F
F
F
F
Wavelength (nm)
N
N
2
1
OMe
O
500
550
600
650
700
Wavelength (nm)
(b)
N
N
300
250
200
150
100
50
N
N
B
3
O
O
B
3
O
F
O
F
F
F
N
N
N
N
4
Chart 1. Structures of compounds 1e4.
4. Experimental section
4.1. Chemicals
11
The known compounds 3 and 4, were prepared by following the
literature method.20 Compounds 13 and 14 were prepared by fol-
lowing the reported procedures.9 THF and toluene were dried over
sodium benzophenone ketyl and chloroform dried over calcium
hydride prior to use. BF3$OEt2 and 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ) obtained from Spectrochem (India) were
used as obtained. All other chemicals used for the synthesis were
reagent grade unless otherwise specified. Column chromatography
was performed on silica (60e120 mesh) or alumina.
0
500
550
600
650
Wavelength (nm)
Fig. 4. A comparison of Q and Soret band (inset) absorption spectra of dyad 7 (—) and
triad 11 (d) recorded in CHCl3. The concentration used for Q-band was 1ꢂ10ꢁ5 M and
for Soret band was 1ꢂ10ꢁ6 M. (b) Comparison of emission spectra of BODIPY monomer
3 (d) and triad 11 (—) at lex 488 nm recorded in CHCl3.
(a)
(b)
4.2. Instrumentation
1H NMR spectra (
d in ppm) were recorded using Varian VXR
300, 400 MHz and Bruker 400 MHz spectrometer. 13C NMR
spectra were recorded on Bruker operating at 100.6 MHz 19F NMR
spectra were recorded on Bruker operating at 376.4 MHz 11B
NMR spectra were recorded on Bruker operating at 128.3 MHz.
TMS was used as an internal reference for recording 1H (of re-
sidual proton;
d d 77.0 signal) in CDCl3. Absorption
7.26) and 13C (
(c)
and steady state fluorescence spectra were obtained with Per-
kineElmer Lambda-35. Fluorescence spectra were recorded at
25 ꢀC in a 1 cm quartz fluorescence cuvette. The fluorescence
quantum yields (FF) were estimated from the emission and ab-
sorption spectra by comparative method at the excitation
wavelength of 488 nm using Rhodamine 6G (Ff¼0.88)18 for
compounds 7/8 and 11/12 as standard. Cyclic voltammetric (CV)
and differential pulse voltammetric (DPV) studies were carried
out with electrochemical system utilizing the three electrode
configuration consisting of a glassy carbon (working electrode),
platinum wire (auxillary electrode), and saturated calomel (ref-
erence electrode) electrodes. The experiments were done in dry
dichloromethane using 0.1 M tetrabutylammonium perchlorate
as supporting electrolyte. Half wave potentials were measured
using DPV and also calculated manually by taking the average of
the cathodic and anodic peak potentials. The ES-MS mass spectra
were recorded with a Q-Tof micro mass spectrometer. High-
2.0 1.5 1.0 0.5 0.0 -0.5 -1.0 -1.5 -2.0
potential (V)
Fig. 5. Comparison of cyclic voltammograms (a) 1, (b) ZnTPP, and (c) 5 in dichloro-
methane containing 0.1 M TBAP as supporting electrolyte recorded at 50 mV/s scan
speed.

T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
837
OMe
N
N
N
N
N Zn
N
N
N
B
Zn
O
O
N
F
F
N
N
N
9
O
N
N
N
N
N
Zn
N
N
B
O
Zn
N
O
N
F
F
N
N
N
10
OMe
CO
N
N
OC
N
N
N Ru
N
N
N
B
O
Ru
O
N
F
F
N
N
N
11
O
CO
N
N
OC
N
N
N
Ru
N
N
B
O
Ru
N
O
N
F
F
N
N
N
12
Chart 2. Structures of triads 9e12.
resolution mass spectrum was obtained from Q-TOF instrument
by electron spray ionization (ESI) technique.
compounds 2 and 6 were obtained on slow evaporation of n-
hexane/dichloromethane over a period of one week. The intensity
data collection for compounds 6 and 2 have been carried out on
a Nonius MACH3 four circle diffractometer at 293 K. Structure
solutions for the compounds 6 and 2 were obtained using direct
methods (SHELXS-97)26 and refined using full-matrix least-
squares methods on F2 using SHELXL-97.27 Compound 2 crystal-
lizes with two molecules in the asymmetric unit. There are no
4.3. X-ray diffraction studies
The *.cif files were deposited with the Cambridge Crystallo-
graphic Data Centre and the following codes were allocated: 2
(CCDC-824841) and 6 (CCDC-824842). The single crystals of

838
T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
Table 4
127.41, 128.02, 128.32, 130.33, 131.08, 134.07, 139.70, 142.88, 146.95,
147.69, 148.47, 151.26, 165.13.
Electrochemical data for compounds 1e12 recorded in dichloromethane containing
0.1 M TBAP as supporting electrolyte recorded at 50 mV/s scan speed
Compound
Oxidation
Reduction
4.4. General synthesis for dyads 5, 6 and triads 9, 10
I
II
I
II
III
The dyads 5/6 and triads 9/10 were synthesized by treating
1 equiv of appropriate BODIPY (1e4) with one and 2 equiv, re-
spectively, of ZnTPP in CHCl3 and stirred under inert atmosphere at
room temperature for 30 min. The solvent was removed on rotary
evaporator under vacuo and the crude solids were recrystallized
twice from CHCl3/n-hexane to afford purple crystalline solids in
55e70% yields.
3
4
1
2
1.28
1.25
d
ꢁ0.913
ꢁ0.789
ꢁ0.888
ꢁ0.672
d
d
ꢁ1.53
ꢁ1.69
d
d
d
d
d
d
d
d
ZnTPP
RuTPP
5
6
7
8
9
10
11
12
0.77
1.08
1.43
1.11
1.11
1.42
1.40
1.08
1.14
1.42
1.41
ꢁ1.35
d
ꢁ1.71
ꢁ1.59
ꢁ1.68
ꢁ1.70
ꢁ1.54
ꢁ1.52
ꢁ1.70
ꢁ1.70
ꢁ1.56
ꢁ1.49
0.870
0.800
0.800
0.916
0.908
0.796
0.792
0.920
0.912
d
ꢁ0.852
ꢁ0.720
ꢁ0.896
ꢁ0.708
ꢁ0.860
ꢁ0.724
ꢁ0.972
ꢁ0.768
ꢁ1.32
ꢁ1.34
d
d
4.4.1. Dyad 5. The compound 5 was obtained as purple solid in 68%
ꢁ1.32
ꢁ1.34
d
yield. IR (KBr, cmꢁ1) 668, 701, 771, 1027, 1121, 1217, 1441, 3019; 1H
NMR (400 MHz, CDCl3,
pyridyl), 3.95 (3H, s, OMe), 4.29 (1H, d, J¼3.9 Hz,
(1H, m, pyridyl), 6.50 (2H, s,
-pyþpyridyl), 6.69 (1H, d, J¼4.5 Hz,
py), 6.87 (1H, d, J¼3.3 Hz, -py), 7.05 (2H, d, J¼7.3 Hz, BODIPY Ar),
7.38 (2H, d, J¼7.9 Hz, BODIPY Ar), 7.65e7.75 (13H, m, AreN4þ -py),
d
in ppm): 3.30 (1H, s, pyridyl), 3.43 (1H, s,
d
b-py), 5.85e5.88
b
b-
b
b
statistically significant differences in the metrical parameters for
the two molecules.
8.16 (8H, d, J¼7.3 Hz, AreN4), 8.84 (8H, s,
b
-py-ZnTPP). 19F NMR
(376.4 MHz, CDCl3,
(128.3 MHz, CDCl3,
(100 MHz, CDCl3,
d
in ppm): ꢁ147.48 (q, JBeF¼56.4 Hz). 11B NMR
d
in ppm): 0.24 (t, JBeF¼29.5 Hz). 13C NMR
4.3.1. 3-(3-Oxypyridine)-8-(4-methoxyphenyl)-4,4-difluoro-4-bora-
3a,4a-diaza-s-indacene 1. The compound 1 was synthesized by
treating the 3-bromo boron dipyrromethene 13 (100 mg,
0.26 mmol) with 3-hydroxypyridine (38 mg, 0.39 mmol) in
CH3CN (15 mL) in the presence of Cs2CO3 (129 mg, 0.39 mmol)
under nitrogen atmosphere at refluxing temperature for 1 h. The
progress of the reaction was followed by TLC analysis, which
showed the disappearance of starting precursors and appearance
of new spot corresponding to the desired compound. The crude
compound was subjected to silica gel column chromatography
using petroleum ether/CH2Cl2 (20:80) and afforded compound 1
as orange solid in 70% yield (72 mg). Rf (20% pet. ether/CH2Cl2)
0.43; IR (KBr, cmꢁ1) 668, 706, 838, 982, 1030, 1122, 1215, 1356,
1443, 1560, 1605, 1749, 2840, 3019; 1H NMR (400 MHz, CDCl3,
d
in ppm): 55.64, 103.98, 114.18, 117.33, 120.85,
123.18, 125.80, 126.49, 127.35, 127.43, 128.83, 129.28, 131.92, 132.32,
133.79, 134.78, 135.94, 140.59, 143.43, 144.83, 149.57, 150.19, 161.88,
162.36. ES-MS mass calcd for C65H44BF2N7O2Zn 1068.65 found
1068.70 [M]þ.
4.4.2. Dyad 6. The compound 6 was obtained as purple solid in 65%
yield. IR (KBr, cmꢁ1) 669, 701, 776, 1022, 1125, 1213, 1445, 3019; 1H
NMR (400 MHz, CDCl3,
2.93 (1H, d, J¼4.3 Hz, pyridyl), 4.24 (1H, d, J¼4.3 Hz,
5.70e5.74 (1H, m, pyridyl), 6.39 (1H, d, J¼8.3 Hz, pyridyl),
6.52e6.53 (1H, m,
-py), 6.72 (1H, s, f2), 6.99 (1H, d, J¼3.0 Hz, f1),
7.17 (1H, d, J¼4.3 Hz, -py), 7.32 (1H, d, J¼3.9 Hz, -py), 7.69 (13H,
m, AreN4þ
(8H, s,
d
in ppm): 2.72 (1H, d, J¼2.1 Hz, pyridyl),
b-py),
b
b
b
b
-py), 7.82 (1H, s, f3), 8.17 (8H, d, J¼6.5 Hz, AreN4), 8.81
d
in ppm): 3.90 (3H, s, OMe), 5.76 (1H, d, J¼4.0 Hz,
b
b
-py), 6.51
-py), 7.02
b
-py-ZnTPP). 19F NMR (376.4 MHz, CDCl3,
d
d
in ppm): ꢁ149.12
(1H, s, -py), 6.68 (1H, s,
b
b
-py), 6.94 (1H, d, J¼4.0 Hz,
(q, JBeF¼26.3 Hz). 11B NMR (128.3 MHz, CDCl3,
in ppm): 0.11 (t,
d in ppm): 104.28, 113.22,
(2H, d, J¼8.0 Hz, BODIPY Ar), 7.39e7.43 (1H, m, pyridyl), 7.49
JBeF¼28.2 Hz). 13C NMR (100 MHz, CDCl3,
(2H, d, J¼8.0 Hz, BODIPY Ar), 7.65 (1H, d, J¼7.31 Hz, pyridyl),
117.34, 119.15, 121.01, 123.20, 126.57, 127.44, 128.01, 131.13, 132.00,
133.64, 134.74, 135.86, 140.30, 140.69, 143.29, 147.15, 150.25. ES-MS
mass calcd for C62H40BF2N7O2Zn 1028.41 found 1028.43 [M]þ.
7.80 (1H, s,
b
-py), 8.56 (1H, d, J¼4.0 Hz, pyridyl), 8.67 (1H, s,
pyridyl). 19F NMR (376.4 MHz, CDCl3,
d
in ppm): ꢁ147.6 (q,
JBeF¼56.4 Hz). 11B NMR (128.3 MHz, CDCl3,
d
in ppm): 0.24 (t,
in ppm): 55.62,
JBeF¼28.2 Hz). 13C NMR (100 MHz, CDCl3,
d
4.4.3. Triad 9. The compound 9 was obtained as purple crystalline
104.68, 114.14, 116.99, 124.61, 125.90, 128.17, 128.24, 129.77,
132.24, 133.69, 134.07, 139.91, 142.82, 144.37, 147.61, 151.18,
161.80, 165.18. HRMS mass calcd for C21H16BF2N3O2 392.1380
found 392.1382 [Mþ1]þ.
solid in 70% yield. IR (KBr, cmꢁ1) 666, 700, 772, 1026, 1120, 1215,
1445, 3020; 1H NMR (400 MHz, CDCl3,
d
in ppm): 3.20 (4H, br s,
pyridyl), 4.01 (3H, s, eOMe), 4.27 (2H, d, J¼4.0 Hz, -py), 5.79 (2H,
b
m, pyridyl), 6.40 (2H, d, J¼8.5 Hz, pyridyl), 6.60 (2H, d, J¼4.58 Hz,
b-
py), 7.09 (2H, d, J¼8.5 Hz, BODIPY Ar), 7.28 (2H, d, J¼8.2 Hz, BODIPY
Ar), 7.64e7.70 (24H, m, AreN4), 8.16 (16H, d, J¼6.7 Hz, AreN4), 8.85
4.3.2. 3-(3-Oxypyridine)-8-(2-furyl)-4,4-difluoro-4-bora-3a,4a-di-
aza-s-indacene 2. Compound 2 was prepared by treating 3-bromo
boron dipyrromethene 14 (100 mg, 0.29 mmol) with 3-hydrox-
ypyridine (42 mg, 0.44 mmol) under same reaction conditions
mentioned for compound 1 and obtained as green solid in 61% yield
(63 mg). Rf (25% pet. ether/CH2Cl2) 0.48; IR (KBr, cmꢁ1) 667, 701,
892, 932, 1084, 1123, 1296, 1356, 1443, 1475, 1560, 1605, 2840, 3017;
(16H, s,
b
-py-N4). 19F NMR (376.4 MHz, CDCl3,
d
in ppm): ꢁ149.16
(q, JBeF¼26.3 Hz). 11B NMR (128.3 MHz, CDCl3,
d
in ppm): 0.34 (t,
JBeF¼26.9 Hz). 13C NMR (100 MHz, CDCl3,
d in ppm): 55.62, 104.68,
114.14, 116.99, 124.61, 125.90, 128.17, 128.24, 129.77, 132.24, 133.69,
134.07, 139.91, 142.82, 144.37, 147.61, 151.18, 161.80, 165.18. ES-MS
mass calcd for C111H71BF2N12O3Zn2 1800.21 found 1800.24 [M]þ.
1H NMR (400 MHz, CDCl3,
6.54 (1H, m, f2), 6.68 (1H, s,
(1H, d, J¼3.9 Hz, -py), 7.40e7.43 (1H, m, pyridyl), 7.49 (1H, d,
-py), 8.57
d
in ppm): 5.81 (1H, d, J¼4.5 Hz,
b-py),
b
-py), 7.07 (1H, d, J¼3.3 Hz, f1), 7.28
4.4.4. Triad 10. The compound 10 was obtained as purple crystal-
b
line solid in 66% yield. IR (KBr, cmꢁ1) 667, 702, 773,1029,1122, 1215,
J¼4.5 Hz, py), 7.65e7.67 (1H, m, pyridyl), 7.81 (2H, s, f3þ
b
1443, 3019; 1H NMR (400 MHz, CDCl3,
d
in ppm): 4.23 (4H, s, pyr-
-py), 6.07e6.10 (2H, m, pyridyl), 6.62
(2H, d, J¼7.3 Hz, pyridyl), 6.73 (1H, s, f2), 6.85 (1H, d, J¼2.9 Hz, f1),
7.10 (2H, d, J¼4.02 Hz, -py), 7.61e7.69 (24H, m, AreN4), 7.81 (1H, s,
(1H, d, J¼4.8 Hz, pyridyl), 8.67 (1H, d, J¼2.7 Hz, pyridyl). HRMS
idyl), 4.62 (2H, d, J¼4.02 Hz,
b
mass calcd for C18H12BF2N3O2 352.1056 found 352.1069 [Mþ1]þ. 19F
NMR (376.4 MHz, CDCl3,
NMR (128.3 MHz, CDCl3,
d
in ppm): ꢁ149.12 (q, JBeF¼26.3 Hz). 11
B
b
d
in ppm): 0.11 (t, JBeF¼28.2 Hz). 13C NMR
f3), 8.14 (16H, d, J¼6.6 Hz, AreN4), 8.83 (16H, s,
b
-py-N4). 19F NMR
(100 MHz, CDCl3,
d
in ppm): 104.99, 113.14, 117.04, 118.81, 124.68,
(376.4 MHz, CDCl3,
d
in ppm): ꢁ149.19 (q, JBeF¼56.4 Hz) 11B NMR

T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
839
(128.3 MHz, CDCl3,
(100 MHz, CDCl3,
d
in ppm): 0.35 (t, JBeF¼28.2 Hz). 13C NMR
calcd for C116H75BF2N12O5Ru2 1968.41 found 1969.52 [Mþ1]þ;
HRMS mass calcd 1969.4210 found 1969.4236 [Mþ1]þ.
d
in ppm): 102.8, 112.4, 117.2, 124.18, 124.5, 126.0,
127.3, 127.7, 130.2, 142.1, 142.5, 146.0, 146.7, 151.4, 162.2. ES-MS mass
calcd for C114H75BF2N12O3Zn2 1840.95 found 1841.95 [Mþ1]þ.
4.5.4. Triad 12. The compound 12 was obtained as red solid in 60%
yield. Rf (75% pet. ether/CH2Cl2) 0.40; IR (KBr, cmꢁ1) 668, 702, 757,
1008, 1130, 1216, 1427, 1596, 1949, 2854, 2926, 3019; 1H NMR
4.5. General synthesis for dyads 7, 8 and triads 11, 12
(400 MHz, CDCl3, d in ppm): 1.42e1.45 (4H, m, pyridyl), 3.66 (2H, d,
The dyads 7/8 and triads 11/12 were synthesized by heating the
mixture of appropriate BODIPY (1e4) with 1 and 2 equiv, re-
spectively, of RuTPP(CO)(EtOH) at 80 ꢀC for 24 h under nitrogen
atmosphere. The progress of the reaction was followed by TLC
analysis, which showed almost complete disappearance of starting
precursors and indication of formation of required dyads 7/8 and
triads 11/12. The crude compounds were subjected to silica gel
column chromatographic purification using petroleum ether/
CH2Cl2 (4:6) and afforded dyads 7/8 and triads 11/12 as red solids in
w60% yields.
J¼4.7 Hz,
b
-py), 5.22e5.26 (2H, dd, J1¼J2¼8.2 Hz, pyridyl), 5.98 (2H,
d, J¼8.2 Hz, pyridyl), 6.78 (1H, s, f2), 6.81 (1H, d, J¼3.5 Hz, f1), 7.04
(2H, d, J¼4.3 Hz,
b-py), 7.49e7.52 (8H, m, AreN4), 7.62e7.72 (16H,
m, AreN4), 7.87 (1H, s, f3), 7.90 (8H, d, J¼7.4 Hz, AreN4), 8.16 (8H, d,
J¼7.1 Hz, AreN4), 8.56 (16H, s,
b
-py-N4). 19F NMR (376.4 MHz,
CDCl3,
CDCl3,
d
d
in ppm): ꢁ149.46 (q, JBeF¼56.4 Hz). 11B NMR (128.3 MHz,
in ppm): 0.57 (t, JBeF¼27.3 Hz). 13C NMR (100 MHz, CDCl3,
d
in ppm): 102.90, 112.98, 117.98, 120.81, 123.53, 126.10, 126.45,
127.28, 129.03, 130.67, 131.89, 134.81, 137.52, 142.28, 143.54, 146.63,
147.86, 150.19, 150.42, 160.86 ES-MS mass calcd for
C113H71BF2N12O5Ru2 1928.80 found 1928.81 [M]þ; HRMS mass
calcd 1929.3897 found 1929.3907 [Mþ1]þ.
4.5.1. Dyad 7. The compound 7 was obtained as red solid in 59%
yield. Rf (50% pet. ether/CH2Cl2) 0.50; IR (KBr, cmꢁ1) 668, 758, 928,
1130, 1215, 1951, 2927, 3019; 1H NMR (400 MHz, CDCl3,
d
in ppm):
1.41 (1H, s, pyridyl), 1.48 (1H, d, J¼5.1 Hz, pyridyl), 3.56 (1H, d,
J¼4.3 Hz, -py), 3.97 (3H, s, OMe), 5.29e5.32 (1H, m, pyridyl), 6.10
(1H, d, J¼8.3 Hz, pyridyl), 6.55 (1H, s, -py), 6.63 (1H, d, J¼4.3 Hz,
py), 6.90 (1H, d, J¼3.1 Hz, -py), 7.07 (2H, d, J¼8.3 Hz, BODIPY Ar),
7.33 (2H, d, J¼8.3 Hz, BODIPY Ar), 7.51e7.55 (8H, m, AreN4),
7.65e7.72 (17H, m, AreN4þ -py), 7.95 (8H, d, J¼7.13 Hz, AreN4),
Acknowledgements
b
M.R. thanks Department of Atomic Energy (DAE) for financial
support and T.K.K. thanks Indian Institute of technology for the
fellowship. We thank the DST-funded National Single Crystal X-ray
Diffraction Facility for diffraction data.
b
b-
b
b
8.18 (8H, d, J¼6.34 Hz, AreN4), 8.58 (16H, s,
b
-py-N4). 19F NMR
Supplementary data
(376.4 MHz, CDCl3,
(128.3 MHz, CDCl3,
(100 MHz, CDCl3,
d
in ppm): ꢁ147.6 (q, JBeF¼56.4 Hz). 11B NMR
d
in ppm): 0.24 (t, JBeF¼28.2 Hz). 13C NMR
Copies of mass, NMR, absorption, fluorescence spectra, cyclic
voltammograms of selected compounds, and X-ray crystallographic
data of compounds 2 and 6 in CIF format. Supplementary data as-
sociated with this article can be found, in the online version, at
doi:10.1016/j.tet.2011.11.048.
d in ppm): 55.73, 103.40, 114.21, 117.25, 121.75,
122.43,125.83,126.50,126.67,127.43,128.58,129.38,132.05,132.30,
133.80, 134.24, 134.36, 137.57, 140.37, 141.50, 142.60, 143.76, 144.66,
148.39, 161.91, 162.64. ES-MS mass calcd for C66H44BF2N7O3Ru
1133.26 found 1134.72 [Mþ1]þ; HRMS mass calcd 1134.2688 found
1134.2679 [Mþ1]þ.
References and notes
1. Imamura, T.; Fukushima, K. Coord. Chem. Rev. 2000, 198, 133e156.
2. Wojaczynski, J.; Latos-Grazynski, L. Coord. Chem. Rev. 2000, 204, 113e171.
3. Beletskaya, I.; Tyurin, V. S.; Tsivadze, A. Y.; Guilard, R.; Stern, C. Chem. Rev. 2009,
109, 1659e1713.
4.5.2. Dyad 8. The compound 8 was obtained as red solid in 58%
yield. Rf (55% pet. ether/CH2Cl2) 0.44; IR (KBr, cmꢁ1) 668, 702, 757,
928, 1130, 1216, 1306, 1427, 1949, 2927, 3019; 1H NMR (400 MHz,
4. Tashiro, K.; Aida, T. Chem. Soc. Rev. 2007, 36, 189e197.
5. Stulz, E.; Scott, S. M.; Bond, A. D.; Teat, S. J.; Sanders, J. K. M. Chem.dEur. J. 2003,
9, 6039e6048.
6. Iengo, E.; Zangrando, E.; Alessio, E. Eur. J. Inorg. Chem. 2003, 2371e2384.
7. Metselaar, G. A.; Ballester, P.; de Mendoza, J. New J. Chem. 2009, 33, 777e783.
8. Rao, M. R.; Mobin, S. M.; Ravikanth, M. Tetrahedron 2010, 66, 1728e1734.
9. Rajeswara Rao, M.; Kumar, K. V. P.; Ravikanth, M. J. Organomet. Chem. 2010, 695,
863e869.
10. Rajeswara Rao, M.; Bolligarla, R.; Butcher, R. J.; Ravikanth, M. Inorg. Chem. 2010,
49, 10606e10616.
11. Madhu, S.; Rao, M. R.; Shaikh, M. S.; Ravikanth, M. Inorg. Chem. 2011, 50,
4392e4400.
CDCl3,
pyridyl), 3.66 (1H, d, J¼4.5 Hz,
6.10 (1H, d, J¼8.0 Hz, pyridyl), 6.56e6.57 (1H, m,
f1), 6.99 (1H, d, J¼3.1 Hz, f2), 7.15 (2H, d, J¼4.6 Hz,
J¼3.5 Hz, -py), 7.54e7.65 (8H, m, AreN4), 7.67e7.74 (17H, m,
AreN4þ -py), 7.85 (1H, s, f3), 7.95 (8H, d, J¼7.5 Hz, AreN4),
d
in ppm): 1.44 (1H, d, J¼2.6, pyridyl), 1.48 (1H, d, J¼5.4 Hz,
-Py), 5.29e5.33 (1H, m, pyridyl),
-py), 6.75 (1H, m,
-py), 7.36 (1H, d,
b
b
b
b
b
8.15e8.19 (8H, m, AreN4), 8.59 (16H, s,
b
-py-N4). 19F NMR
(376.4 MHz, CDCl3,
(128.3 MHz, CDCl3,
d
in ppm): ꢁ149.10 (q, JBeF¼26.3 Hz). 11B NMR
in ppm): 0.12 (t, JBeF¼28.2 Hz). ES-MS mass
d
calcd for C63H40BF2N7O3Ru 1093.23 found 1094.28 [Mþ1]þ; HRMS
12. Loudet, A.; Burgess, K. Chem. Rev. 2007, 107, 4891e4932.
13. Ziessel, R.; Ulrich, G.; Harriman, A. New J. Chem. 2007, 31, 496e501.
14. Ulrich, G.; Ziessel, R.; Harriman, A. Angew. Chem., Int. Ed. 2008, 47, 1184e1201.
mass calcd 1093.2297 found 1093.2264 [M]þ.
ꢁ
15. Baruah, M.; Qin, W.; Basaric, N.; De Borggraeve, W. M.; Boens, N. J. Org. Chem.
4.5.3. Triad 11. The compound 11 was obtained as red solid in 62%
yield. Rf (65% pet. ether/CH2Cl2) 0.38; IR (KBr, cmꢁ1) 669, 758, 928,
2005, 70, 4152e4157.
16. Baruah, M.; Qin, W.; Vallee, R. A. L.; Beljonne, D.; Rohand, T.; Dehaen, W.; Boens,
ꢁ
N. Org. Lett. 2005, 7, 4377e4380.
1130, 1216, 1950, 2927, 3019; 1H NMR (400 MHz, CDCl3,
d
in ppm):
17. Qin, W.; Leen, V.; Dehaen, W.; Cui, J.; Xu, C.; Tang, X.; Liu, W.; Rohand, T.;
Beljonne, D.; Averbeke, B. V.; Clifford, J. N.; Driesen, K.; Binnemans, K.; Au-
weraer, M. V. D.; Boens, N. J. Phys. Chem. C 2009, 113, 11731e11740.
18. Qin, W.; Leen, V.; Rohand, T.; Dehaen, W.; Dedecker, P.; Van der Auweraer, M.;
Robeyns, K.; Van Meervelt, L.; Beljonne, D.; Van Averbeke, B.; Clifford, J. N.;
Driesen, K.; Binnemans, K.; Boens, N. J. Phys. Chem. A 2009, 113, 439e447.
19. Rohand, T.; Qin, W.; Boens, N.; Dehaen, W. Eur. J. Org. Chem. 2006, 4658e4663.
20. Khan, T. K.; Rao, M. R.; Ravikanth, M. Eur. J. Org. Chem. 2010, 2314e2323.
21. Kee, H. L.; Kirmaier, C.; Yu, L.; Thamyongkit, P.; Youngblood, W. J.; Calder, M. E.;
Ramos, L.; Noll, B. C.; Bocian, D. F.; Scheidt, W. R.; Birge, R. R.; Lindsey, J. S.;
Holten, D. J. Phys. Chem. B 2005, 109, 20433e20443.
1.43 (4H, s, pyridyl), 3.56 (2H, d, J¼4.02 Hz,
b-py), 5.23e5.29 (2H, m,
pyridyl), 6.01 (2H, d, J¼8.8 Hz, pyridyl), 6.56 (2H, d, J¼4.58 Hz,
b-
py), 7.09 (2H, d, J¼7.8 Hz, BODIPY Ar), 7.16 (2H, d, J¼7.6 Hz, BODIPY
Ar), 7.49 (8H, d, J¼6.84 Hz, AreN4), 7.63e7.76 (16H, m, AreN4), 7.90
(8H, d, J¼6.6 Hz, AreN4), 8.17 (8H, d, J¼6.6 Hz, AreN4), 8.55 (16H, s,
b
-py-N4). 19F NMR (376.4 MHz, CDCl3,
d
in ppm): ꢁ149.38 (q,
in ppm): 0.39 (t,
d in ppm): 22.6, 55.82,
JBeF¼56.4 Hz). 11B NMR (128.3 MHz, CDCl3,
d
JBeF¼29.5 Hz). 13C NMR (100 MHz, CDCl3,
22. Kim, K.; Jo, C.; Easwaramoorthi, S.; Sung, J.; Kim, D. H.; Churchill, D. G. Inorg.
101.62, 114.25, 121.75, 122.36, 125.12, 125.49, 126.47, 126.66, 127.41,
128.01, 128.42, 129.23, 131.07, 132.03, 132.21, 134.21, 134.38, 134.98,
137.40, 141.20, 142.67, 143.78, 148.59, 160.60, 180.48. ES-MS mass
Chem. 2010, 49, 4881e4894.
23. Darling, S. L.; Mak, C. C.; Bampos, N.; Feeder, N.; Teat, S. J.; Sanders, J. K. M. New
J. Chem. 1999, 23, 359e364.

840
T.K. Khan, M. Ravikanth / Tetrahedron 68 (2012) 830e840
24. Kojima, T.; Nakanishi, T.; Honda, T.; Harada, R.; Shiro, M.; Fukuzumi, S. Eur. J.
Inorg. Chem. 2009, 727e734.
26. Sheldrick, G. M. SHELXS-97, Program for Crystal Structure Solution; University of
€
€
Gottingen: Gottingen, Germany, 1997.
25. Quan-Guo, W.; Seik-Weng, N.; Wei-Hong, Z.; Yong-Shu, X. Chin. J. Struct. Chem.
27. Sheldrick, G. M. SHELXL-97, Program for Crystal Structure Refinement; University
€
€
2010, 29, 1197e1200.
of Gottingen: Gottingen, Germany, 1997.